A patient adapter makes it possible to mechanically couple an eye to be treated to a laser apparatus, for example. In this way, the eye can be positioned accurately with respect to the laser apparatus in the direction of propagation of the laser beam emitted by the laser apparatus (this direction is often referred to as a z-direction). In a laser treatment of the eye with the goal of making an incision (cut) in the eye by means of the laser beam, it is necessary to have information of the z-position of the eye in a coordinate system of the laser apparatus. The patient adapter makes it possible to secure the eye in relation to the laser apparatus in the z-direction and thus creates a prerequisite for an accurate application of the incision in the eye in the z-direction.
A conventional example of a patient adapter is designed in two parts and comprises a suction ring and a conical spacer. The suction ring can be placed on the eye and affixed to the eye by suction force. The conical spacer can be coupled to the laser apparatus and has an applanation plate in the region of a narrow cone end. The applanation plate provides a contact surface for the eye and is transmissive for laser radiation. A plurality of suction spaces are at least partially delimited by the suction ring, and a corresponding number of flexible evacuation hoses are provided to connect each suction space with a vacuum pump apparatus. One end of each hose is attached to the suction ring and an opposite end of each hose attached to a connection port at the vacuum pump apparatus. A first of the suction spaces is delimited entirely by the suction ring and is open towards the eye, so that the first suction space can be closed by placing the suction ring on the eye. By subsequently evacuating the first suction space, the suction ring can be affixed to the eye. A second suction space is delimited by both the suction ring and the conical spacer, and evacuation of the second suction space permits to hold the conical spacer in close coupling engagement with the suction ring.
With the conventional patient adapter, the suction ring is initially placed on the eye by the surgeon and is affixed there by applying a vacuum to the first suction space. The conical spacer is in turn mounted on the laser apparatus. In this phase, the suction ring and the spacer are still completely separate from one another. Next, there is a relative approach of the eye with the suction ring sitting on it, on the one hand, and the spacer, which is held on the laser apparatus, on the other hand, until the spacer enters an insertion funnel formed on the suction ring. Finally, a vacuum is created in the second suction space to draw the spacer axially against the suction ring. After bringing the spacer closer to the suction ring by suction, the surface of the eye is leveled off by the applanation plate. In this condition, a cut can be made in the eye tissue, for example, in the cornea, by means of laser radiation of the laser apparatus.